This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Safety/Efficacy Study of Seqirus A/H7N9 IIV With or Without MF59(R) Adjuvant to Prevent Avian Influenza (NCT03682120), a randomized phase 2 study. The primary outcome is Geometric Mean Titers (GMT) of Serum Hemagglutinin Inhibition (HAI) Antibodies.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03682120 |
| Phase | Phase 2 |
| Condition | Avian Influenza, Influenza Immunisation |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Double |
| Enrollment | 372 |
| Arms in the primary outcome | 4 |
| Lead sponsor | National Institute of Allergy and Infectious Diseases (NIAID) |
| Results posted | Yes |
2. Clinical Question
Population
The trial enrolled healthy males and non-pregnant females aged 18–64 years who met the eligibility criteria. The primary endpoint analysis used the modified intent-to-treat population: participants who received at least one study vaccination and had pre-vaccination and at least one post-vaccination blood sample with valid HAI assay results.
Intervention
Participants received two intramuscular doses of the 2017 A/H7N9 inactivated influenza vaccine on Day 1 and Day 22. Three groups received vaccine with MF59 adjuvant, at 3.75 mcg, 7.5 mcg, or 15 mcg per dose.
Comparator
The fourth group received 15 mcg per dose of the same vaccine without MF59 adjuvant. The arm descriptions list planned group sizes of N=106 for each adjuvanted group and N=53 for the unadjuvanted group. The primary endpoint results use available valid assay results, with analysis counts that differ from those planned group sizes.
Primary question
At Day 43, approximately 21 days after the second dose, what were the serum HAI antibody geometric mean titers in each group, and how precisely were those estimates measured? The posted primary results provide arm-specific estimates and 95% confidence intervals. A formal primary between-group analysis is not reported in the registry record.
The trial addressed both safety and immune response. Its primary endpoint was a laboratory measure of antibody response, rather than a clinical measure of influenza infection or prevention. The posted results therefore describe antibody titers after vaccination in the analyzed participants; they do not by themselves establish how well vaccination would prevent illness.
3. Trial Design
The registry record describes a completed, randomized, double-blind, parallel-group Phase II study. The stated enrollment was 372. The trial compared three doses of A/H7N9 inactivated influenza vaccine given with MF59 adjuvant against a 15 mcg dose given without adjuvant. All groups were scheduled to receive two intramuscular doses on Day 1 and Day 22. Phosphate buffered saline diluent could be used to achieve targeted dosages.
The study was designed to assess safety, reactogenicity, and immunogenicity. The primary antibody endpoint was measured at Day 43, which the endpoint description identifies as 21 days after the second dose. The brief summary also describes assessment of HAI and neutralizing antibody responses. The registry lists 41 outcome measures and 28 posted secondary outcomes. The displayed primary results include arm-level HAI geometric mean titers; the secondary results include antibody thresholds and seroconversion measures at Day 22.
The arm descriptions list planned group sizes of N=106 in each adjuvanted group and N=53 in the unadjuvanted group. Analysis counts vary by outcome, reflecting the results available for the relevant measure. For the primary HAI outcome, the analysis population is defined by vaccination and availability of valid pre- and post-vaccination blood test results, rather than simply by the planned arm size.
The registry record gives a start date of 2018-11-02 and a primary completion date of 2020-04-30, and marks the study completed. The brief summary describes a study lasting approximately 17 months and participant participation lasting approximately 13 months. Details of the randomization procedure, allocation concealment, and the statistical analysis plan are not reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Overall Study
| Stage | 3.75 mcg A/H7N9+MF59 | 7.5 mcg A/H7N9+MF59 | 15 mcg A/H7N9+MF59 | 15 mcg A/H7N9 |
|---|---|---|---|---|
| STARTED | 105 | 105 | 105 | 57 |
| COMPLETED | 92 | 97 | 97 | 55 |
| NOT COMPLETED | 13 | 8 | 8 | 2 |
Reasons for not completing this period:
| Reason | 3.75 mcg A/H7N9+MF59 | 7.5 mcg A/H7N9+MF59 | 15 mcg A/H7N9+MF59 | 15 mcg A/H7N9 |
|---|---|---|---|---|
| Lost to Follow-up | 11 | 4 | 5 | 2 |
| Physician Decision | 1 | 0 | 0 | 0 |
| Withdrawal by Subject | 1 | 2 | 3 | 0 |
| Death | 0 | 1 | 0 | 0 |
| Enrolled but Treatment Not Administered | 0 | 1 | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: The modified intent-to-treat (mITT) population includes all participants who received at least one study vaccination and contributed both pre- and at least one post-study vaccination venous blood samples for HAI antibody assays for which valid results were reported.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
Population: The baseline analysis population includes all enrolled participants
| Characteristic | Unit | 3.75 mcg A/H7N9+MF59 | 7.5 mcg A/H7N9+MF59 | 15 mcg A/H7N9+MF59 | 15 mcg A/H7N9 | Total |
|---|---|---|---|---|---|---|
| Participants analysed | 105 | 105 | 105 | 57 | 372 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 105 | 105 | 105 | 57 | 372 |
| Age, Categorical: >=65 years | Participants | 0 | 0 | 0 | 0 | 0 |
| Age, Continuous | years | 39.1 (SD 13.6) | 40.5 (SD 13.7) | 38.8 (SD 13.3) | 43.8 (SD 15.1) | 40.2 (SD 13.8) |
| Sex: Female, Male: Female | Participants | 59 | 63 | 65 | 29 | 216 |
| Sex: Female, Male: Male | Participants | 46 | 42 | 40 | 28 | 156 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 7 | 6 | 10 | 3 | 26 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 98 | 99 | 95 | 54 | 346 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 7 | 6 | 3 | 4 | 20 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 17 | 12 | 16 | 13 | 58 |
| Race (NIH/OMB): White | Participants | 78 | 81 | 82 | 37 | 278 |
| Race (NIH/OMB): More than one race | Participants | 2 | 4 | 2 | 2 | 10 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 1 | 2 | 2 | 1 | 6 |
| Region of Enrollment: United States | participants | 105 | 105 | 105 | 57 | 372 |
| Prior Seasonal Influenza Vaccination (2017-2018 or 2018-2019): Neither | Participants | 17 | 18 | 23 | 14 | 72 |
| Prior Seasonal Influenza Vaccination (2017-2018 or 2018-2019): 2017-2018 Only | Participants | 10 | 8 | 8 | 4 | 30 |
| Prior Seasonal Influenza Vaccination (2017-2018 or 2018-2019): 2018-2019 Only | Participants | 17 | 14 | 14 | 6 | 51 |
| Prior Seasonal Influenza Vaccination (2017-2018 or 2018-2019): Both 2017-2018 and 2018-2019 | Participants | 61 | 65 | 60 | 33 | 219 |
6. Primary Endpoint
The registry lists the primary outcome as Geometric Mean Titers (GMT) of Serum Hemagglutinin Inhibition (HAI) Antibodies, measured over Day 43.
| Element | Registry entry |
|---|---|
| Result type | Geometric Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | titer |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the geometric mean titer of serum hemagglutinin inhibition antibodies at Day 43. HAI testing measures whether antibodies in a blood sample inhibit the influenza virus’s ability to agglutinate red blood cells. In this trial, the assay used the 2017 H7N9 vaccine virus as its antigen. Each sample was tested at least twice according to the laboratory’s standard operating procedure, and the geometric mean of the replicate results was used as the sample’s result. The arm-level geometric mean was then calculated from the available results.
A geometric mean is a way to summarize measurements that are positive and may vary multiplicatively. It is calculated on a logarithmic scale and returned to the original scale, so it is not the same as an ordinary arithmetic average. The endpoint’s 95% confidence interval communicates uncertainty around each arm’s estimate. It helps indicate the precision of the measured antibody response, but does not itself test whether groups differ.
Antibody titers are used as immunogenicity measures because they quantify a laboratory response to vaccination. They are not, on their own, direct counts of infections prevented or clinical cases avoided. The registry record reports an HAI antibody endpoint and a separate neutralizing antibody assessment; the primary result concerns HAI titers at Day 43.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
At Day 43, the reported HAI geometric mean titer was 23.3 for the 3.75 mcg A/H7N9+MF59 group (95% CI 17.9 to 30.3), 19.9 for the 7.5 mcg A/H7N9+MF59 group (95% CI 15.8 to 25.1), and 24.2 for the 15 mcg A/H7N9+MF59 group (95% CI 18.8 to 31.1). For the 15 mcg unadjuvanted group, the estimate was 6.0 (95% CI 5.6 to 6.6). These are arm-specific summaries of the available valid HAI results in the modified intent-to-treat population.
The three adjuvanted-group confidence intervals overlap. The unadjuvanted group’s interval does not overlap the intervals of the adjuvanted groups. Such visual comparisons can describe how the estimates and their uncertainty relate, but interval overlap is not a substitute for a prespecified statistical comparison. The registry record does not report a formal primary comparison, an adjusted estimate of a between-group difference, or a primary-endpoint p-value. The displayed estimates therefore support a descriptive reading, not a definitive claim about a treatment contrast.
The observed pattern is that the three adjuvanted dose groups had similar-looking arm-level GMT estimates, while the unadjuvanted group’s estimate was lower. The values alone do not establish a dose-response relationship, nor do they isolate the effect of MF59 from every other possible explanation. Although the 15 mcg dose appears in both an adjuvanted and an unadjuvanted group, an inferential comparison between those groups is not reported for the primary endpoint. The trial’s randomization and masking are design features, but they do not remove the need to know the analysis plan and the results of the planned comparison when interpreting a treatment contrast.
The confidence intervals describe precision of the arm-level estimates under the analysis used. They do not capture every source of uncertainty, including limitations in the analysis population or any unreported details of the assay and statistical procedures. The analysis counts for the primary outcome were 102, 101, 101, and 55 across the groups. These differ from the planned group sizes in the arm descriptions, and the endpoint population definition explains that valid blood test results were required. The registry record does not report why each participant’s result was unavailable or whether missingness differed systematically between groups.
Overall, the posted primary result is an immunogenicity description at a specified time after vaccination. It is not a direct estimate of vaccine effectiveness against avian influenza. The registry record does not report a clinical infection-prevention endpoint in these results, and the antibody GMTs should not be interpreted as a direct measure of clinical benefit.
9. Statistical Methods Explained
The primary endpoint is continuous on a titer scale and is summarized with a geometric mean and a 95% confidence interval for each arm. The laboratory calculated a geometric mean of replicate assay results for each sample, then calculated the arm-level geometric mean from the available results. This approach is suitable for positive biological measurements that are naturally interpreted on a multiplicative scale. It prevents a small number of high values from dominating the summary in the same way they could affect an arithmetic mean, although the exact distribution of individual titers is not included in the registry record.
What does a confidence interval describe?
In general, a confidence interval expresses the statistical uncertainty around an estimate under the method used to calculate it. A narrower interval indicates greater precision in that estimate; a wider interval indicates less precision. The interval is not a range that contains every participant’s result, nor does it measure all possible sources of uncertainty. The primary results report 95% confidence intervals for each arm’s GMT. They do not report a confidence interval for a primary between-arm contrast.
Arm-specific estimates answer a descriptive question: what was the estimated antibody titer in each group? A causal or inferential comparison asks a different question: how much did outcomes differ between groups, and how uncertain is that difference? That second question ordinarily requires a specified contrast and an analysis method. A formal primary comparison and its statistical plan are not reported in the registry record. Consequently, the arm estimates should not be presented as if they were a reported hypothesis test.
What does the analysis population mean?
The primary analysis uses a modified intent-to-treat population. It includes participants who received at least one vaccination and contributed both pre-vaccination and at least one post-vaccination venous blood sample for HAI assays with valid results. This definition retains a connection to the randomized groups while requiring assay data for the outcome. It also means the primary analysis does not necessarily include every randomized participant. The analysis counts are specific to this outcome and should not be assumed to apply to every safety or secondary endpoint.
When data are unavailable, the analysis population and handling of missing results matter. Excluding participants without valid assay results can affect estimates if the availability of results is related to antibody response, vaccination, or other characteristics. The registry record gives the population definition but does not report the reasons for missing or invalid results, a missing-data strategy, or sensitivity analyses. It is therefore not possible to determine from the record whether missingness could have changed the estimates.
How should the secondary comparisons be read?
The posted secondary outcomes include percentages of participants meeting antibody thresholds and measures of seroconversion. A percentage is a binary-outcome summary: each participant either meets the stated criterion or does not. A risk difference expresses the difference between two proportions on the absolute scale. The secondary comparison calculations are unadjusted, and the registry lists no reported analyses for those measures. They should therefore be regarded as exploratory calculations rather than as documented, prespecified sponsor analyses.
For a binary endpoint with few observed events, estimates can be unstable and confidence intervals can be wide. A result of zero observed events in an arm does not establish that the underlying probability is zero. Likewise, a small p-value from an unadjusted comparison does not on its own establish a reliable finding. Interpretation should consider the confidence interval, the number of endpoints and comparisons examined, and whether the analysis was planned in advance. The registry record does not report a multiplicity adjustment or the full analysis plan.
What are the planning illustrations?
The planning illustrations use the observed effect as a starting point and show hypothetical participants per arm for specified power levels and fractions of that effect. Their stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. They are not the trial’s own design justification, and they are not observed power. They do not show the probability that the completed trial detected an effect, nor do they establish which effect size is scientifically important. The registry record does not report the original sample-size justification or its assumptions.
In general, planning calculations depend on the effect to be detected, outcome variability or event frequency, significance level, allocation, and desired power. If a planning effect is taken from a noisy observed result, the illustration may not represent the effect expected in a future study. The different fractions displayed are scenarios, not evidence that any particular effect is established. Their interpretation should remain separate from the outcomes observed in this trial.
Over-dispersion is a general concern for count data when variability is greater than a simple model assumes; it can make standard errors too small if the model does not account for it. The primary endpoint is a titer summary, not a count outcome, and no over-dispersion model is described in the registry record. The record also does not report model diagnostics, transformation details beyond the geometric-mean calculation, or whether any covariate adjustment was used. These omissions limit assessment of the analysis beyond the reported summary statistics.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists many outcome measures and secondary outcomes. Examining multiple endpoints, time points, and group comparisons raises the possibility that some nominally unusual results arise by chance, even when no underlying difference exists. Statistical methods can address this issue by defining a hierarchy of outcomes, adjusting significance thresholds, or treating secondary analyses as exploratory. The registry record does not report a multiplicity adjustment, a testing hierarchy, or a statistical analysis plan that specifies how the many outcomes were to be interpreted. The displayed secondary comparison calculations are unadjusted and should not be read as confirmatory findings.
The record defines the modified intent-to-treat population for the primary HAI endpoint as participants who received at least one vaccination and had valid pre-vaccination and post-vaccination assay results. This is important because participants without valid outcome measurements are not represented in the endpoint analysis. The primary arm analysis counts are 102, 101, 101, and 55. Reasons for absent or invalid results, the number excluded for each reason, and the handling of missing data are not reported in the registry record.
The record does not report whether an interim analysis was planned or conducted, whether the primary analysis used covariate adjustment, or how departures from the stated analysis population were handled. These details should not be inferred from the completed status or from the posted estimates. The lack of reported analysis details does not show that procedures were absent; it means their use cannot be established from the registry record.
For a complete assessment, readers would need the prespecified analysis plan and fuller reporting of participant flow, missing assay results, endpoint-specific populations, multiplicity procedures, and any interim analyses. Without those details, the primary GMTs remain interpretable as descriptive arm-level results, while secondary comparisons warrant particular caution.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| 3.75 mcg A/H7N9+MF59 | 1 | 105 | 1.0% |
| 7.5 mcg A/H7N9+MF59 | 6 | 105 | 5.7% |
| 15 mcg A/H7N9+MF59 | 4 | 104 | 3.8% |
| 15 mcg A/H7N9 | 1 | 57 | 1.8% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| 3.75 mcg A/H7N9+MF59 | 0 of 105 |
| 7.5 mcg A/H7N9+MF59 | 1 of 105 |
| 15 mcg A/H7N9+MF59 | 0 of 104 |
| 15 mcg A/H7N9 | 0 of 57 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| 3.75 mcg A/H7N9+MF59 | 93 of 105 |
| 7.5 mcg A/H7N9+MF59 | 95 of 105 |
| 15 mcg A/H7N9+MF59 | 92 of 104 |
| 15 mcg A/H7N9 | 45 of 57 |
Most frequent serious adverse event terms
| Event term | Organ system | 3.75 mcg A/H7N9+MF59 | 7.5 mcg A/H7N9+MF59 | 15 mcg A/H7N9+MF59 | 15 mcg A/H7N9 |
|---|---|---|---|---|---|
| Pneumonia | Infections and infestations | 0 of 105 | 1 of 105 | 0 of 104 | 1 of 57 |
| Bradycardia | Cardiac disorders | 0 of 105 | 0 of 105 | 1 of 104 | 0 of 57 |
| Vertigo | Ear and labyrinth disorders | 0 of 105 | 0 of 105 | 1 of 104 | 0 of 57 |
| Cholecystitis | Hepatobiliary disorders | 0 of 105 | 1 of 105 | 0 of 104 | 0 of 57 |
| Appendicitis | Infections and infestations | 0 of 105 | 1 of 105 | 0 of 104 | 0 of 57 |
| Chlamydial Infection | Infections and infestations | 0 of 105 | 0 of 105 | 1 of 104 | 0 of 57 |
| Anastomotic Ulcer | Injury, poisoning and procedural complications | 0 of 105 | 0 of 105 | 1 of 104 | 0 of 57 |
| Multiple Injuries | Injury, poisoning and procedural complications | 0 of 105 | 1 of 105 | 0 of 104 | 0 of 57 |
| Cervical Spinal Stenosis | Musculoskeletal and connective tissue disorders | 0 of 105 | 1 of 105 | 0 of 104 | 0 of 57 |
| Neck Pain | Musculoskeletal and connective tissue disorders | 0 of 105 | 1 of 105 | 0 of 104 | 0 of 57 |
Most frequent non-serious adverse event terms
| Event term | Organ system | 3.75 mcg A/H7N9+MF59 | 7.5 mcg A/H7N9+MF59 | 15 mcg A/H7N9+MF59 | 15 mcg A/H7N9 |
|---|---|---|---|---|---|
| Injection Site Pain (Tenderness) | General disorders | 75 of 105 | 74 of 105 | 71 of 104 | 16 of 57 |
| Injection Site Pain | General disorders | 48 of 105 | 43 of 105 | 46 of 104 | 6 of 57 |
| Fatigue | General disorders | 35 of 105 | 33 of 105 | 36 of 104 | 11 of 57 |
| Headache | Nervous system disorders | 34 of 105 | 31 of 105 | 29 of 104 | 14 of 57 |
| Myalgia | Musculoskeletal and connective tissue disorders | 18 of 105 | 23 of 105 | 22 of 104 | 7 of 57 |
| Malaise | General disorders | 16 of 105 | 21 of 105 | 21 of 104 | 10 of 57 |
| Injection Site Erythema | General disorders | 21 of 105 | 14 of 105 | 13 of 104 | 8 of 57 |
| Upper Respiratory Tract Infection | Infections and infestations | 11 of 105 | 16 of 105 | 16 of 104 | 5 of 57 |
| Injection Site Induration | General disorders | 12 of 105 | 14 of 105 | 14 of 104 | 4 of 57 |
| Nausea | Gastrointestinal disorders | 9 of 105 | 9 of 105 | 13 of 104 | 5 of 57 |
Serious events with the highest arm-level rate: pneumonia (1.8%), bradycardia (1.0%), vertigo (1.0%), chlamydial infection (1.0%), anastomotic ulcer (1.0%).
The registry safety summaries distinguish serious adverse events from other adverse events. Serious adverse events were reported for 1 of 105 participants in the 3.75 mcg A/H7N9+MF59 group, 6 of 105 in the 7.5 mcg A/H7N9+MF59 group, 4 of 104 in the 15 mcg A/H7N9+MF59 group, and 1 of 57 in the 15 mcg A/H7N9 group. The corresponding counts for other adverse events were 93 of 105, 95 of 105, 92 of 104, and 45 of 57. Deaths were reported as 0, 1, 0, and 0 across those groups, respectively.
These are descriptive counts with the stated at-risk denominators. They do not establish that an event was caused by vaccination, and the registry record does not report event relatedness in the registry record for these summaries. The serious-event terms listed include Pneumonia at 1.8%, and Bradycardia, Vertigo, Chlamydial Infection, Anastomotic Ulcer, and Invasive Ductal Breast Carcinoma at 1.0% each. Such terms describe reported events, not necessarily vaccine-related events.
Small group sizes and sparse serious events limit precision in comparing groups. The safety summaries should be read separately from antibody results; neither set of results establishes a treatment effect on the other.
12. What the Result Does, and Does Not, Mean
The results describe HAI antibody responses after two doses of A/H7N9 inactivated influenza vaccine, administered with or without MF59 adjuvant, in healthy adults aged 18–64 years. They show arm-specific Day 43 geometric mean titers and confidence intervals, alongside a set of secondary immunogenicity outcomes and descriptive safety counts. The primary GMT estimates were higher in the adjuvanted groups than in the unadjuvanted group, while the three adjuvanted-group estimates were relatively close to one another. These are descriptions of the posted data, not proof of a statistically established group difference.
The record does not report a formal primary between-group test or an adjusted contrast. It also does not report a primary p-value. Without those analyses, the arm-level values cannot establish the size or statistical certainty of an effect attributable to adjuvant or dose. Confidence intervals help describe precision for each arm’s estimate, but they do not answer every comparative question.
The endpoint is an antibody measure, not a clinical endpoint such as infection, illness, or prevention. A measured immune response does not by itself show how many cases would be avoided or whether a response corresponds to clinical protection. No such clinical effect should be inferred from the GMTs or antibody thresholds in this record.
The secondary results broaden the immunogenicity description but are subject to uncertainty from sparse outcomes and the many measures examined. Their unadjusted comparisons are exploratory, and a multiplicity plan is not reported. Missing or invalid assay results and their handling are also not fully described. Safety findings are likewise descriptive: event counts do not establish causation, and the available record does not state whether the listed events were considered related to study vaccination.
In sum, the registry results offer a measured account of antibody responses and reported adverse events in the analyzed groups. They do not provide a complete inferential comparison, establish clinical effectiveness, or settle the interpretation of every secondary or safety finding.
13. Why This Trial Matters Statistically
This trial illustrates the difference between reporting outcome summaries and answering a comparative statistical question. A geometric mean and its confidence interval describe an antibody response within each group. A treatment comparison requires an explicit contrast, its uncertainty, and an analysis appropriate to the trial design. The registry record gives the arm-level primary results but does not report a formal primary comparison. Readers should not treat differences between displayed arm estimates as though they were the result of a documented primary hypothesis test.
It also highlights why analysis populations matter. The primary endpoint uses a modified intent-to-treat definition requiring valid blood samples before and after vaccination. The resulting analysis counts differ from the planned group sizes. This is not inherently evidence of bias, but it makes participant flow and reasons for unavailable results relevant to interpretation. Those details are not reported in the registry record.
Multiplicity is another important statistical issue. The study lists many outcome measures and posted secondary outcomes. Unadjusted findings among a large set of comparisons are less persuasive than a clearly prespecified primary result, especially when response events are uncommon and estimates are uncertain. The registry does not report a multiplicity strategy or a hierarchy that would distinguish confirmatory from exploratory outcomes.
Finally, the endpoint measures immunogenicity rather than clinical prevention. Keeping that distinction clear prevents laboratory findings from being overstated as evidence about illness outcomes. Together, these features make the record useful for understanding the trial’s measured antibody responses while also showing why a full protocol, statistical analysis plan, and complete participant accounting are important for rigorous interpretation.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
Several limitations specific to this trial affect interpretation. First, the primary results are arm-level HAI GMTs without a reported formal primary comparison. The estimates can be described, but the registry record does not establish inferential evidence for differences between dose or adjuvant groups. The absence of a reported comparison also prevents assessment of its prespecified estimand or adjustment method.
Second, the primary analysis requires valid pre- and post-vaccination blood test results. The reported analysis counts differ from the planned group sizes, but the registry record does not explain why results were unavailable or invalid, nor does it report missing-data sensitivity analyses. The secondary outcome counts also vary by measure. This makes endpoint-specific participant availability important when comparing results across outcomes.
Third, the registry lists many outcome measures, but a multiplicity plan and statistical analysis plan are not reported. Secondary comparisons are unadjusted, and reported analyses are not listed for the secondary outcomes described. They should be treated as exploratory rather than as a collection of confirmatory tests.
Fourth, the primary outcome and secondary antibody measures are laboratory endpoints. The registry results do not report clinical infection or prevention outcomes, so antibody findings cannot establish clinical effectiveness. The safety summaries are also descriptive; event attribution and relatedness are not reported in the available record.
Finally, details of randomization implementation, allocation concealment, assay handling beyond the stated replicate testing, covariate adjustment, and interim analyses are not reported in the registry record. These gaps do not demonstrate that relevant procedures were not used, but they limit independent appraisal of the methods and the full uncertainty around the results.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Safety/Efficacy Study of Seqirus A/H7N9 IIV With or Without MF59(R) Adjuvant to Prevent Avian Influenza — NCT03682120.
- Registry record last updated 2021-05-17; status last verified 2018-09-13.
- Results first posted 2021-05-17.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
The registry record describes a completed, randomized, double-blind, parallel-group Phase II study of A/H7N9 inactivated influenza vaccine in healthy adults aged 18–64 years. It lists enrollment of 372 and compares three adjuvanted dose groups with a 15 mcg unadjuvanted group. Participants were scheduled for two intramuscular doses on Day 1 and Day 22.
The primary outcome was serum HAI antibody geometric mean titer at Day 43, analyzed in a modified intent-to-treat population requiring valid pre- and post-vaccination assay results. The record reports arm-level GMT estimates and 95% confidence intervals, but no formal primary between-group analysis. Secondary immunogenicity outcomes and descriptive safety findings are also posted. Multiplicity procedures, a complete statistical analysis plan, and detailed missing-data handling are not reported in the registry record.